Xerographic plate transporting mechanism

ABSTRACT

AN IMPROVED MECHANISM FOR TRANSPORTING A FLAT XEROGRAPHIC PLATE THROUGH A POWDER IMAGE TRANSFER STATION HAVING MEANS FOR EQUALIZING THE LINEAR VELOCITIES OF THE PLATE TRANSFORMING MECHANISM AND THE SUPPORT SHEET FEEDING MECHANISM IN THE TRANSFER STATION, THE VELOCITY EQUALIZING MEANS BEING POSITIONED ADJACENT THE PATH OF TRAVEL OF THE XEROGRAPHIC PLATE ALONG THE PLANE PASSING ALONG THE IMAGE-BEARING SURFACE OF THE XEROGRAPHIC PLATE. IN THE PARTICULAR EMBODIMENTS DESCRIBED, THE VELOCITY EQUALIZING MEANS COMPRISES A RACK SUPPORTED BY THE PLATE TRANSPORTING MECHANISM, A GEAR SEGMENT SUPPORTED BY THE SUPPORT SHEET FEEDING MECHANISM AND MEANS TO PERMIT THE MOTOR DRIVING THE PLATE TRANSPORTING MECHANISM OR THE MOTOR DRIVING THE SUPPORT SHEET FEEDING MECHANISM TO OVERDRIVE THE OTHER OF SAID MOTORS.

June 27, 1972 A. LUNNING ETAL 3,672,760

XEROGRAPHIC PLATE TRANSPORTING MECHANISM Filed Sept. 28, 1970 :5 Shuts-Sheet 2 June 27, 1972 LUNNING ETAL XEROGRAPHIC PLATE TRANSPORTING MECHANISM 3 Shuts-Sheet 3 Filed Sept. 28, 1970 Q NW MR L. 1).)? mfi w E 00 0 o a U a WIPQ a W m W Wm wh Wm United States Patent Office 3,672,750 Patented June 27, 1972 U.S. Cl. 355-3 19 Claims ABSTRACT OF THE DISCLOSURE An improved mechanism for transporting a fiat xerographic plate through a powder image transfer station having means for equalizing the linear velocities of the plate transporting mechanism and the support sheet feeding mechanism in the transfer station, the velocity equalizing means being positioned adjacent the path of travel of the xerographic plate along the plane passing along the image-bearing surface of the xerographic plate. In the particular embodiments described, the velocity equalizing means comprises a rack supported by the plate transporting mechanism, a gear segment supported by the support sheet feeding mechanism and means to permit the motor driving the plate transporting mechanism or the motor driving the support sheet feeding mechanism to overdrive the other of said motors.

BACKGROUND OF THE INVENTION This invention relates to the field of xerography and, more particularly, to a mechanism for transporting a xerographic plate through an automated fiat-plate xerographic processing system.

In the xerographic process as described in Carlson U.S. No. 2,297,69l a base plate of relatively low electrical resistance, such as metal, having a photoconductive insulator layer coated thereon is electrostatically charged in the dark. The charged coating is then exposed to a light image. The charges leak off rapidly to the base plate in proportion to the intensity of light to which any given area is exposed, the charge being substantially retained in nonexposed areas. After such exposure, the coating is contacted with electroscopic marking particles in the dark. When forming a positive image, these particles adhere to the areas where the electrostatic charges remain whereby there is formed a xerographic powder image corresponding to the latent electrostatic image. The powder image can then be transferred to a sheet of transfer material resulting in a positive print having excellent detail and quality. Alternatively, when the base plate is relatively inexpensive, as in the case of paper, it may be desirable to fix the powder image directly to the plate itself and thereby eliminate the image transfer operation.

The art of xerography, as briefly described above, is also amenable to recording X-ray patterns such as might be attained by passing X-rays through a body to be analytically examined. The art of X-ray recording by xerography, generally known as xerodiography, relates to the recording of X-ray patterns and information by means of materials and devices whose electrical conductivity is altered by the action of X-rays reaching the recording medium. In xerodiography, the plate or element exposed to the X-ray pattern usually comprises a metallic backing sheet having a photoconductive insulator layer or coating, for example vitreous selenium, on one surface thereof. It is conventional to cover or protect the photoconductive coating from ambient light by a slide plate, usually called a dark slide, spaced from the photoconductice surface. The plate or element is sensitized by applying a uniform electrostatic charge to the coating and thereafter the charged plate is exposed to sensitizing radiation with the object to be examined appropriately interposed between the radiation source and the sensitized plate. Under influence of the X-rays emanating from the source which are differentially absorbed by different areas of the test body, but which readily pass through the dark slide, the photoconductive coating becomes electrically conductive in those portions reached by the sensitizing radiation, thereby permitting portions of the electrostatic charge thereon to be selectively dissipated. Dissipation of the electrostatic charge is proportional to the amount of radiation absorbed by the test body with greater dissipation occurring in those portions of the coating shaded by less absorptive portions of the object being radiographed. In this manner, an electrostatic latent image of the test body is formed on the photoconductive element. The image may then be made visible with an electroscopic marking material which clings to the electrostatically charged portion of the latent image. Reversible, or negative, prints can also be developed by contacting the latent electrostatic image with marking particles of the same polarity. The xeroradiographic process is disclosed, for example, in Schalfert et a1. U.S. No. 2,666,144.

It has previously been recognized that xeroradiography can be applied to the field of medical diagnostics. For example, the xeroradiographic process when utilized to examine extremities, such as hands and feet, has been characterized as being a valuable diagnostic technique since more information is recorded on the xeroradiogram than is recorded on a corresponding radiogram.

In recent years, the xerodiographic technique has been utilized in the early detection and diagnosis of breast cancer in women. The process, known as xeromammography, has been described as requiring less radiation than non-screen film radiology, and one which gives greater detail in the mammogram to be reviewed by the radiologist. Additionally, a most important advantage is in the increased ease and speed of interpretation of the xeromammogram. Because they are easier to interpret and, accordingly, reduce the fatigue on the examining radiologist, thereby increasing his overall effectiveness, the technique is believed to have application in screening techniques for the early detection of breast cancer.

In application Ser. No. 874,747, filed Nov. 7, 1969, and assigned to the assignee of the present invention, there is described an automated flat-plate xerographic processing system including charging means for placing a uniform electrostatic charge on the photoconductive surface of a xerographic plate, means for holding a lighttight cassette into which the xerographic plate can be inserted, means for opening the cassette and for inserting the charged xerographic plate therein without exposing the charged plate to actinic electromagnetic radiation, means for receiving the xerographic plate-holding cassette after imaging exposure, the xerographic plate having thereon a latent electrostatic image suitable for subsequent development, means for opening the cassette and for withdrawing the latent electrostatic image-bearing xerographic plate from the cassette without further exposure of the xerographic plate to actinic electromagnetic radiation, means for developing the latent electrostatic image to form a reproduction thereof suitable for visual examination, and means for advancing the xerographic plate to the developing means without disturbing the latent electrostatic image thereon. In this system, exposure of the uniformly charged xerographic plate takes place outside of the xerographic processing apparatus. This feature enables the radiologist, when considering medical examinations, to selectively position a patient, and particularly those portions of the patients body being examined, with respect to the radiation source and the xerographic plate. To permit such exposure outside the processing apparatus, the processing system described in the aforementioned co-pending application includes a light-tight cassette into which the uniformly charged xerographic plate is inserted and through which imaging exposure is made. To complete the xerographic processing cycle, the toner image on the photoconductive surface of the xerographic plate is transferred to a suitable support member. This is generally achieved by withdrawing a single support sheet from a supply tray, transporting it to a point where it is in registration with the xerographic plate having the powder image thereon, transferring the powder image to the support sheet, and transporting the support sheet with the powder image thereon to fuser means from which the xerographic reproduction is advanced into a receiving tray. When using a non-reusable photoconductive element (such as zinc oxide coated paper), the need to transfer the powder image to a further support sheet is eliminated.

In the aforementioned co-pending application, the xerographic plate is advanced through the two processing units by numerous transport mechanisms. With respect to the unit wherein conditioning and electrostatic charging of the xerographic plate takes place, separate mechanisms Where provided for withdrawing the xerographic plate from its storage box and for inserting the leading edge of the xerographic plate into the conditioning means, for transporting the xerographic plate through the conditioning means, for withdrawing the xerographic plate from the conditioning means and for depositing the xerographic plate upon the plate carriers in the plate storage magazine, for withdrawing the bottom-most xerographic plate from the storage magazine, for transporting the xerographic plate along a path beneath the electrostatic charging means and for inserting the charged xerographic plate into a cassette.

With respect to the processing unit wherein the latent electrostatic image residing on the photoconductive surface of the xerographic plate is converted into a corresponding powder image which is subsequently transferred to a separate support sheet, distinct mechanisms were provided for withdrawing the latent electrostatic imagebearing xerographic plate from the cassette, for positioning the xerographic plate above the development means, for transporting the xerographic plate, after development, from its position above the developing means to a position where it is in registration with a separate support sheet, for transporting the xerographic plate in registration with the separate support sheet, for transporting the xerographic plate, after the powder image has been transferred therefrom to the support sheet, along a path where a cleaning brush rotates in contact with the photoconductive surface of the xerographic plate, and for inserting the cleaned xerographic plate into a storage box.

The overwhelming number of plate transporting mechanisms initially provided required that they be reduced in number. Accordingly the vastly improved plate transporting mechanism, described in application Ser. No. 68.098, filed on Aug. 31, 1970, was designed. As described therein, the plate transporting mechanism engages a fiat xerographic plate at a first terminal position and transports it completely to a second terminal position where it is deposited for storage, inserted into a cassette or storage box, or deposited for certain xerographic processing. In this manner, the numerous plate transporting mechanisms have been reduced to four, two in each of the two processing units associated with the automated system described above.

As indicated above, in the second of the two units, the latent electrostatic image residing on the photoconductive surface of the xerographic plate is converted into a corresponding powder image which is thereafter transferred to a separate support sheet. In the transfer station, the support sheet is brought into virtual contact with the powder image-bearing surface of the xerographic plate. Under well-known electrostatic principles, the xerographic powder image is transferred, in perfect registration, from the xerographic plate to the adjacent surface of the support sheet. To achieve such faithful transfer, it is necessary that the xerographic plate and the support sheet be moving at essentially the same linear velocity during the image transfer. This requirement cannot be positively assured with the improved plate transporting mechanism referred to above which, although adequate for three of the plate transporting operations, 'is not, accordingly, suitable for transporting the xerographic plate through the transfer station. It would, therefore, be desirable to have a plate transporting mechanism, employing the principle described in application Ser. No. 68,098, for smoothly converting continuous unidirectional motion of the drive means into two-directional movement of the plate transporting mechanism along the single horizontal plane, and capable of assuring that the xerographic plate and the support sheet adjacent thereto in the transfer station will have substantially the same linear velocity along the transfer plane, whereby faithful transfer can be achieved.

OBJECTS OF THE INVENTION It is, therefore, the primary object of the present invention to provide a further improved mechanism for transporting a flat xerographic plate through an automated xerographic processing system.

It is a further object of the present invention to provide an improved mechanism for transporting a flat, imagebearing xerographic plate in registration with a support sheet in a transfer station.

It is a further object of the present invention to provide an improved flat xerographic plate transporting mechanism which supports the xerographic plate in the transfer plane but enables the transporting mechanism to cooperate with the support sheet feeding mechanism also along the transfer plane.

It is a further object of the present invention to provide an improved mechanism for transporting a fiat xerographic plate through a transfer station, said mechanism including means for substantially eliminating the difference in linear velocities of the xerographic plate and the adjacent support sheet when they are positioned in powder image transfer adjacency.

It is a further object of the present invention to provide an improved mechanism for transporting a powder imagebearing xerographic plate through a transfer station, said mechanism having means for supporting the xerographic plate in the transfer plane and means adapted to cooperate with the support sheet feeding means to substantially equalize the linear velocities of the xerographic plate and the adjacent support sheet as they pass through the actual powder image transfer zone.

These and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed disclosure.

BRIEF SUMMARY OF THE INVENTION These and still further objects of the present invention are achieved, in accordance therewith, by providing a fiat xerographic plate transporting mechanism having a pair of opposed, vertical shuttle plates, each of the shuttle plates having a substantialy vertical slot therein, endless drive chain means passing over sprocket wheels at each of two terminal positions, means to drive the drive chain means in one direction only, a pin securely mounted on each drive chain associated with the drive chain means and adapted to pass through the substantially vertical slot in each shuttle plate, means, of specific configuration as described below, supported by each shuttle plate to engage the xerographic plate at the first terminal position, means mounted on at least one shuttle plate and adapted to cooperate with means on the support sheet feeding mechanism in the transfer station to equalize the linear velocities of the xerographic plate and the support sheet adjacent thereto when they are positioned in image transfer adjacency, and means to cause the plate engaging means to become disengaged from the xerographic plate at the second terminal position after image transfer and after the xerographic plate is properly supported within the second terminal position.

As described in application Ser. No. 68,098, the drive chain means is adapted to be driven in a single direction only. Each pin secured to a drive chain passes through, and is retained in, the slot in the shuttle plate adjacent thereto. When the drive means is energized, these pins cause the shuttle plates, which carry the plate-engaging means, to be moved from the first terminal position through the transfer station to the second terminal position. When the shuttle mechanism reaches the second terminal position, the pins engage the outer periphery of the sprocket wheels and, with continued movement of the drive chains, the pins are moved either upwardly or downwardly within each slot and, with further continued motion of the drive chains, the plate transporting mechanism is caused to move from the second terminal position back to the first terminal position, without need for reversing the direction of the drive means or the drive chains. A similar, but different directional, reversal of direction occurs at the first terminal position as the pins engage the sprocket wheels and pass about the periphery thereof. Thus, continuous undirectional motion of the drive means (and the drive chains) is smoothly translated into two-directional movement of the plate transporting mechanism along a single horizontal plane which, in this particular instance, has an intermediate processing station, herein referred to as the transfer station.

The plate engaging means of the present invention comprises a pair of pawls pivotally mounted on each shuttle plate. Each pawl includes an elongated leg connected to the pivot point in such a manner as to define an acute angle between the leg and the vertical shuttle plate on which it is mounted. At the end of the elongated leg remote from the pivot point there is a horizontal plate-engaging leg terminating, in its inwardly most position, in a plate-engaging end adapted to enter into properly angled slots or recesses in the side rails of the xerographic plate, whereby the xerographic plate is engaged and advanced from the first terminal position toward the second terminal position. It is thus apparent that the pawls are pivotally mounted either above or below the level of the xerographic plate (i.e., the image transfer plane). The acute angle which each elongated leg makes with respect to the shuttle plate and the length of the elongated leg are so chosen that there is sufficient space between the shuttle plate and that end of the elongated leg connected to the horizontal plate-engaging leg for the velocity equalizing means on the shuttle plate and the support sheet feeding mechanism to be positioned therein for cooperation during the transfer operation. In this manner, the velocity equalizing means are positioned along the image transfer plane, which was not possible with the embodiment described in detail in application Ser. No. 68,098 since the horizontal positioned pawls occupied that position.

In the particular embodiment described herein, the xerographic plate is being transported along a horizontal path. The support sheet, however, is being advanced along an arcuate path which becomes parallel to the xerographic plate within the actual transfer zone adjacent the transfer corotron. After image transfer, the support sheet, having the xerographic powder image thereon, is advanced away from the xerographic plate to fixing means where the powder image thereon is permanently fixed to the support sheet. Since the linear velocity of portions of the support sheet feeding mechanism (or the support sheet itself) will vary as the distance from the center of curvature varies, the linear velocities of the plate transporting mechanism and the support sheet feeding mechanism can be best equalized by initially matching the respective 6 velocities of the two units as close as possible and subsequently identically matching their velocities by cooperating means positioned along the image transfer plane.

The velocity equalizing means, in this particular embodiment, includes a rack supported by at least one shuttle plate along the horizontal plane passing along the imagebearing surface of the xerographic plate (i.e., the image transfer plane). As the shuttle plate reaches the transfer station, the rack thereon comes into contact with a properly positioned gear segment, or pinion, on the support sheet feeding mechanism. As indicated above, this contact is made in the space between the shuttle plate and the edge of the elongated pawl leg most closely adjacent thereto and is along the image transfer plane.

The support sheet feeding mechanism has its own motor which drives the mechanism, and the support sheet fed thereby, in the desired direction relative to the xerographic plate as they pass in virtual contact in the transfer station. To enable the linear velocities of the plate transporting mechanism and the support sheet feeding mechanism to be properly equalized, either the unidirectional motor associated with the plate transporting mechanism or the motor associated with the support sheet feeding mechanism must control and overdrive the combined units when they are brought into contact by means of the rack and gear segment referred to above.

In the embodiment where the plate transporting motor overdrives the support sheet feeding motor, the plate transporting mechanism is driven slightly faster (in a linear velocity sense) than the support sheet feeding mechanism is driven. A clutch mechanism associated with the support sheet feeding motor permits the necessary slippage between the latter motor and the support sheet feeding mechanism whereby the linear velocities are equalized by the support sheet feeding mechanism assuming the linear velocity of the plate transporting mechanism In the embodiment where the support sheet feeding motor overdrives the plate transporting motor, the support sheet feeding mechanism is driven slightly faster than the plate transporting mechanism. The vertical slot in the shuttle plate has a short horizontal leg adjacent the lower end thereof and extending toward the trailing edge of the xerographic plate being supported by the plate transporting mechanism (i.e., the slot becomes an L- shaped slot). Thus, when the velocity equalizing means come into contact in the transfer station, the pin extending into the L-shaped slot will be free to move along the slot as the support sheet feeding motor overdrives the plate transporting motor. The linear velocities of the two units are equalized by the plate transporting mechanism assuming the linear velocity of the support sheet feeding mechanism. After the xerographic plate has passed through the transfer station and the rack supported by the shuttle plate is no longer in contact with the gear segment supported by the support sheet feeding mechanism, the unidirectional motor associated with the plate transporting mechanism causes the pin to be brought against the leading surface of the slot (i.e., the surface most closely adjacent the second terminal position) whereby, with continued movement of the drive chains, the xerographic plate is advanced to, and eventually into, the second terminal position.

In either embodiment, since both mechanisms are moving together in essence as a single unit, neither the xerographic plate nor the support sheet can attain a difference in linear velocity, assuming the absence of xerographic plate or support sheet jams. Faithful transfer of the xerographic powder image from the xerographic plate to the adjacent support sheet is, therefore, more positively assured. The present invention achieves this equalized linear velocity of the two units in the transfer station, and the advantage afforded thereby, without sacrificing the advantages afforded by the use of the plate transporting mechanism and principle broadly described in application Ser. No. 68,098.

BRIEF DESCRIPTION OF THE DRAWINGS The nature of the invention will be more easily understood when it is considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elcvational view of a portion of the improved plate transporting mechanism of the present invention as it reaches the transfer station when the xerographic plate supported thereby is being transported from right to left;

FIG. 2 is an end view of that portion of the plate transporting mechanism shown in FIG. 1, taken along line 22, showing both sides of the mechanism and the Xerographic plate supported therebetween;

FIG. 3 is a side elevational view of an alternative embodiment of the improved plate transporting mechanism of the present invention, also showing the mechanism as it reaches the transfer station when the xcrographic plate supported thereby is being transported from right to left; and

FIGS. 4 and 5 are side views showing the cooperation of switching means, associated with the support sheet feeding mechanism, with the positioning cam means, adjacent the leading edge of the plate transporting mechanism. whereby the support sheet feeding mechanism is actuated and caused to move in proper synchronization with the plate transporting mechanism of FIG. 3.

In describing the present invention with regard to the figures identified above, it should be understood that only one-half of the plate transporting mechanism of the present invention has been shown. The corresponding elements on the opposite side of the plate transportation path are, in these particular embodiments, mirror images of the elements more particularly described in the figures.

The manner in which the plate transporting mechanism of the present invention is caused to change direction is more particularly described in aforementioned application Ser. No. 68,098. As indicated above, the plate transporting mechanism of the present invention has been particularly designed for use in conjunction with an automated xerographic processing system of the type described in application Ser. No. 874,834, filed Nov. 7, 1969, both of these applications being assigned to the assignee of the present invention. Portions of said co-pending applications which are necessary for a complete understanding of the present invention, or to complete the disclosure hereof, are incorporated herein by reference.

Referring to FIGS. 1 and 2, there is seen a plate transporting mechanism which, in this particular instance, is adapted to transport a xerographic plate 12 having side rails 14 from right to left through xerographic powder image transfer station 16. On each side of the plate transportation path there is a vertical shuttle plate 18 adapted to support a flat xerographic plate therebetween, in a manner similar to that shown in application Ser. No. 68,098. As indicated above, the opposed shuttle plate not shown in FIGS. 1 and 2 is a mirror image of the shuttle plate. and the elements supported thereby, actually depicted in these figures. Adjacent the leading edge 20 of the shuttle plate there is an arm or bracket 22 bent inwardly, at a right angle to the shuttle plate, toward the area between the shuttle plates in which the xerographic plate is supported. In a similar manner, adjacent the trailing edge 24 of the shuttle plate there is a further inwardly extended arm or bracket 26. Aligned apertures 28 and 30 in brackets 22 and 26, respectively, have a horizontal bar 32 extending therethrough. Mounted on bar 32 adjacent the leading edge of the shuttle plate is a pawl 34, the bottom end of which is urged inwardly by spring 36 also mounted on bar 32. Adjacent the trailing edge of the shuttle plate pawl 34 is mounted in similar fashion and caused to rotate inwardly by spring 36, The pawls are, therefore, mounted for rotation in a vertical plane, as

8 opposed to the horizontal plane in which the pawls in application Ser. No. 68,098 rotate. Springs 36 and 36 cause the lower portion of the pawls associated therewith to be rotated inwardly until the upper portions 38, or set screws supported thereby, come into contact with the upper portion 40 of shuttle plate 18. The lower portion of pawls 34 and 34 can be rotated toward shuttle plate 18 against the action of springs 36 and 36', respectively, as the edges thereof come into contact with associated elements of the automated xerographic processing system.

Each pawl includes an elongated leg 42 which, as shown, is caused to pivot essentially about the midpoint thereof. At the lower end thereof there is an essentially horizontal plate engaging leg 44 adapted to enter into properly angled slots or recesses in the side rails of the xerographic plate desired to be transported through the transfer station. Though essentially horizontal, leg 44 does have angled surfaces 46 and 48 terminating in apex 50 thereby defining the leg which is adapted to enter into the recesses in the side rails of the xerographic plate.

Pawls 34 and 34' on each shuttle plate 18 are so mounted that they will properly engage the xerographic plate at the first terminal position, suport the xerographic plate between the two terminal positions, and properly disengage from the xerographic plate at the second terminal position. Stationary cam means may or may not be provided, as desired, to achieve desired movement of the pawls, specifically legs 44 thereof, in the two terminal positions. In the particular embodiment described herein, means are provided in each terminal position to prevent the plate transporting mechanism from moving the plate in the wrong direction prior to its reversal of direction (i.e., since the plate will be held stationary, the pawls will be cammed out of plate engagement). In the first terminal position, such means can be a portion of the means which position the xerographic plate on top of the development chamber. After reversal of direction, however, the pawls will engage the appropriate slots in the xerographic plate whereby the plate will be transported from the first terminal position toward the second terminal position. When the plate reaches the second terminal position, the pawls will contact the side walls of the storage box positioned therein and will be cammed out of engagement with the xerographic plate whereby the plate will be deposited within the storage box. Once deposited therein, clips adjacent the slot in the lower front portion of the storage box will prevent the xerographic plate from being withdrawn therefrom after the plate transporting mechanism has reversed direction. An exemplary storage box, having such retaining clips, is shown in FIGS. 4-7 of application Ser. No. 874,834.

Supported on side frame 51 of the Xerographic processing unit is a stationary mmber 52 carrying a ball bearing supporting member 54. Each shuttle plate has rigidly mounted thereon a member 56 which rides on ball bearings 58 supported between members 54 and 56. In this manner, the shuttle plates are mounted on the side frames of the xerographic processing unit for traversing movement between the two terminal positions.

In each terminal position, sprocket wheels 61 on opposed sides of the terminal positions have drive chains 60 passing about the periphery thereof. The plate transporting mechanism of the present invention is caused to move between the two terminal positions by means of unidirectional motor 62 supported out of the plane of xerographic plate travel between the two terminal positions. Unidirectional motor 62 drives the plate transporting mechanism by means of a drive chain passing about sprocket wheels mounted on a drive shaft connected to motor 62 and a drive shaft connected to at least one of the sprocket wheels in one of the two terminal positions.

For the purposes of this discussion, it will be assumed that unidirectional motor 62 causes drive chains 60 to move continuously in a clockwise direction with regard to the shuttle plate 18 actually depicted in FIG. 1. It should be understood, however, that counter-clockwise rotation is not critical since the plate transporting mechanism of the present invention can be made, with minor modifications, to operate with the drive chains moving in a counterclockwise direction.

Each shuttle plate 18 has a vertically extending slot 64 therein. A pin 66 mounted on one of the links associated with each drive chain, is adapted to extend into slot 64 and be retained therein during traversing movement of the plate transporting mechanism. When pin 66 is adjacent the lowermost portion of slot 60 and the drive chain, as shown in FIG. 1, is moving in a clockwise direction, shuttle plate 18 on each side of the plate transporting path will be moved from right to left. When the shuttle plates reach the second terminal position, pins 66 engage the periphery of the sprocket wheels therein and, with continued rotation of the drive chains, are caused to move upwardly within slot 64. Further rotation of the drive chains in the clockwise direction positions the pins at the uppermost portions of slot 64 with the result that the shuttle plates 18 are now caused to move from left to right. At the first terminal position a similar reversal of direction occurs. At the first terminal position, with the particular orientation established in these drawings for purposes of explanation, pins 66 are caused to move about the periphery of the sprocket wheels therein in a downward direction and then in a direction toward transfer station 16. It is in this manner, as set forth in application Ser. No. 68,098, that continuous unidirectional motion of motor 62 and drive chains 60 is smoothly translated into twodirectional motion of the plate transport mechanism along a. single horizontal plane between the two terminal positions.

In the xerographic powder image transfer station 16, support sheet feeding mechanism 70, a portion of which is shown in FIGS. 1 and 2, advances the support sheet to essentially tangential, image-transfer contact with the lower image-bearing surface of the xerographic plate 12. Support sheet feeding mechanism 70, driven by motor 78, is caused to stop in the position substantially as shown in FIGS. 1 and 2 after the mechanism comes in contact with a switch (not shown) which deactuates motor 78. Actually, the support sheet feeding mechanism is permitted to coast to the rest position, as shown, after motor 78 is deactuated. To one side of the support sheet feeding mechanism and directly below rack 72 supported by each shuttle plate 18, there is a gear segment 74, or pinion, having an upwardly extending arm 76 adapted to extend into the path of travel of rack 72 as the xerographic plate is advanced into the transfer station. Because it is permitted to coast to a stop, the support sheet feeding mechanism will not be in the same rest position during each support sheet feeding cycle. That is, arm 76 might vary in position by a fraction of an inch or more. Surface 77 on arm 76, however, provides a positive aligning surface whereby the teeth on rack 72 will be properly aligned with the corresponding grooves on gear segment 74 as they come into contact upon further movement of each shuttle plate 18 into transfer station 16 and rotation of support sheet feeding mechanism 70, supporting gear segment 74, through the transfer position. Thus, to the extent that support sheet feeding mechanism 70 and arm 76 supported thereby stop in slightly different positions during successive support sheet feeding cycles, the cooperation of the leading edge of rack 72 with surface 77 always causes proper engagement of the rack and the gear segment as the two are moved through the transfer station.

Additionally, as rack 72 comes into contact with arm 76 and the support sheet feeding mechanism 70 is caused to rotate slightly in a counter-clockwise direction, motor 78 is actuated thereby causing the feeding mechanism to continue in its counter-clockwise rotation. In this embodiment, the plate transporting motor (i.e. unidirectional motor 62) overdrives the support sheet feeding motor 78; accordingly, the plate transporting mechanism is being driven at a slightly faster rate than is the support sheet feeding mechanism. For example, the plate transporting mechanism can be driven at a rate of about 1.72 inches per second while the support sheet feeding mechanism is being driven at a rate of about 1.63 inches per second, of a difference of about 0.1 inch per second. Clutch means associated with the support sheet feeding motor 78 permits the necessary slippage between motor 78 and support sheet feeding mechanism '70, whereby the support sheet feeding mechanism assumes the linear velocity of the plate transporting mechanism by virtue of rack 72 meshing with gear segment 74 as the plate transporting mechanism passes through transfer station 16. The support sheet fed by mechanism 70 is properly positioned adjacent the imagebearing surface of the xerographic plate. Under wellknown electrostatic principles and using pre-transfer and transfer corotrons, the xerographic powder image is faithfully transferred to the adjacent surface of the support sheet. Thereafter, the image-bearing support sheet follows the path dictated by mechanism 70 which, after image transfer, is away from the path followed by the xerographic plate. Mechanism 70 also feeds the image-bearing support sheet to fixing means where the xerographic powder image is permanently affixed to the support sheet surface.

As can best be seen in FIG. 2, the teeth on rack 72 are adapted to mesh with the corresponding grooves on gear segment 74 along the image transfer plane. i.e., along the plane passing along the lower or image-bearing surface of the xerographic plate. Specifically, the line along which the rack and the gear segment contact each other during image transfer (i.e., the pitch line) is positioned along this image transfer plane. The linear velocity of the support sheet feeding mechanism will, accordingly, be approximately, but not exactly, equal to the linear velocity of the plate transporting mechanism. Identical equalization of the linear velocities is in accordance with the description above. In a similar manner, rack 72 and gear segment 74 in the mechanism shown in FIGS. 35 are also positioned to contact each other along the image transfer plane.

In the embodiment where the support sheet feeding motor overdrives the plate transporting motor. the plate transporting mechanism of FIGS. 3-5 is utilized. With two exceptions, the plate transporting mechanism of FIGS. 3-5 is the same as that depicted in FIGS. 1 and 2: accordingly. like numerals have been utilized in FIG. 3 to represent like elements shown in FIGS. 1 and 2. As shown in FIG. 3, vertical slot 64 has a horizontal leg 82, at the lower end thereof, extending toward trailing edge 26 of the shuttle plate. Additionally, adjacent the leading edge of the shuttle plate there is a downwardly depending leg 84 adapted to contact spring loaded arm 86 on mechanism 70 as the xerographic plate is advanced into the transfer station.

In this embodiment, support sheet feeding mechanism 70 stops in the home position with the leading edge 88 of pinion 74 approximately 20 from the vertical. As can best be seen in FIGS. 4 and 5, when the plate transporting mechanism enters the transfer station. the lower surface of leg 84 contacts the upper surface of pivotally mounted arm 86. This causes arm 86 to be depressed into the position shown in phantom in FIG. 4 whereby the end 90 of arm 86 remote from that end contacting leg 84 closes switch 92. With continued movement of the plate transporting mechanism toward the second terminal position, arm 84 moves past the position where it depresses arm 86 whereby arm 86 is free to rotate upwardly under urging of spring 94. This opens switch 92 which, in turn, actuates support sheet feeding mechanism motor 78. This action properly synchronizes the meshing of the teeth on pinion 74 with the corresponding grooves on rack 72.

In this embodiment, the support sheet feeding mechanism is driven somewhat faster than is the plate transporting mechanism. For example, the support sheet feeding mechanism can be driven at a rate of about 1.60 inches 11 per second while the plate transporting mechanism is driven at a rate of about 1.50 inches per second; once again, a difference of about 0.1 inch per second. When rack 72 and pinion 74 properly mesh, the plate transporting mechanism will assume the linear velocity of the support sheet feeding mechanism which, as indicated above, is slightly faster. This means that the shuttle plates, and the xerographic plates supported thereby, will be moving somewhat faster than its driving means. Accordingly, pin 66 will gradually move toward end 96 of horizontal leg 82 of slot 64 during the period when the support sheet feeding mechanism motor 78 is overdriving unidirectional motor 62. In this manner, the linear velocities of the two units are equalized whereby faithful transfer of the xerographic powder image can be attained. After the xerographic plate has completely passed through the transfer station and rack 72 is no longer in contact with gear segment 74, the plate transporting mechanism will be advanced solely by virtue of its connection to unidirectional motor 62. When this happens, pin 66 moves forward in slot 82 until it once again contacts the leading surface 98 thereof and, by virtue of such contact, causes the continued movement of the plate transporting mechanism toward the second terminal position.

The above embodiment has been described with reference to the orientation where the drive chains 60 are moving in a clockwise direction, when viewing the shuttle plate depicted in FIG. 3 from the interior of the xerographic processing unit. The plate transporting mechanism of the present invention can also be made to operate with the drive chains moving in a counter-clockwise direction; however, leg 82 must be positioned at the upper end of slot 64 but also extending toward the trailing edge of the shuttle plate.

Appropriate microswitches can be provided to stop either the plate transporting mechanism or the support sheet feeding mechanism at any desired home position, for example, after a single cycle as described above. Additionally, means, associated with the support sheet feeding mechanism, are provided to withdraw a single support sheet from a supply of support sheets and advance the support sheet to the appropriate rest position, awaiting movement of the plate transporting mechanism of the present invention into the transfer station.

It should be understood that the present invention has been described with reference to presently preferred embodiments thereof and that other equivalent embodiments are presently contemplated. For example, depending upon the clearances, etc. available, the means by which the shuttle plates are secured to the side frames of the processing unit may be raised or lowered, in conjunction with the raising or lowering of the vertical slot and the drive chains, etc.

While the invention has been described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the true spirit and scope of the invention. Accordingly, all substitutions, additions, and/or modifications of the present invention, or to which the present invention is readily susceptible, without departing from the true spirit and scope of the invention, are considered part of the present invention.

What is claimed is:

1. A mechanism for transporting a flat, powder imagebearing xerographic plate through an image transfer station wherein the powder image is transferred from the xerographic plate to the adjacent surface of a support sheet, said mechanism comprising means to engage a xerographic plate and to transport the xerographic plate through the transfer station, said engaging and transporting means including a pair of shuttle plates having opposed portions between which the xerographic plate is supported, a pair of pawls mounted on each of said shuttle plates for rotation in a plane substantially perpendicular to the path of xerographic plate travel, each of said pawls having a leg at the end thereof remote from said shuttle plate for engaging corresponding recesses in the xerographic plate being transported thereby, each of said shuttle plates and said pawls mounted thereon defining a gap therebetween, means mounted on at least one of said shuttle plates within said gap adjacent thereto along the plane passing along the powder image-bearing surface of the xerographic plate for equalizing the linear velocity of said xerographic plate transporting mechanism and the linear velocity of the support sheet feeding mechanism within the transfer station, whereby the xerographic plate and an adjacent support sheet, fed by the support sheet feeding mechanism into image transfer adjacency, will be moving at the same linear velocity during image transfer, and means to cause said xerographic plate engaging means to become disengaged from the xerographic plate after image transfer.

2. The mechanism of claim 1 wherein the xerographic plate is transported along a horizontal path and said pair of opposed shuttle plates are vertically oriented.

3. The mechanism of claim 1 wherein said pawls are mounted for rotation on said shuttle plate either above or below the plane passing along the powder imagebearing surface of the xerographic plate, thereby enabling said velocity equalizing means to be positioned along said plane within said gap.

4. The mechanism of claim 1 wherein said velocity equalizing means comprises a rack adapted to mesh with a gear segment on the support sheet feeding mechanism, and means permitting the motor driving said plate transporting mechanism or the motor driving the support sheet feeding mechainsm to overdrive the other of said motors.

S. The mechanism of claim 1 wherein said velocity equalizing means comprises a rack adapted to mesh with a gear segment in the support sheet feeding mechanism, and an L-shaped slot in at least one of said shuttle plates, said L-shaped slot having a first leg perpendicular to the image bearing surface of the xerographic plate and a second leg parallel to the image-bearing surface of the xerographic plate, said second leg extending toward the trailing edge of said xerographic plate transporting mechanism said slot adapted to receive a pin freely movable therein, said pin being operatively connected to the drive means associated with said plate transporting mechanism whereby, during image transfer, the velocities of said plate transporting mechanism and the support sheet feeding mechanism are equalized by the movement of said pin within said second leg in a direction opposite to the direction of travel of the xerographic plate.

6. The mechanism of claim 5 wherein said second leg is connected to said first leg adjacent the upper end of said first leg.

7. The mechanism of claim 5 wherein said second leg is connected to said first leg adjacent the lower end of said first leg.

8. The mechanism of claim 1 further including means supported by said plate transporting mechanism for initiating movement of the support sheet feeding mechanism as the plate transporting mechanism is advanced into the transfer station.

9. Means for transferring a xerographic powder image from a flat xerographic plate to the adjacent surface of a support sheet in an image transfer station comprising means to transport a flat powder image-bearing xerographic plate through the transfer station, said transporting means including a pair of shuttle plates having opposed portions between which the xerographic plate is supported, a pair of pawls mounted on each of said said shuttle plates for rotation in a plane substantially perpendicular to the path of xerographic plate travel, each of said pawls being mounted on said shuttle plate at an acute angle thereto, each of said pawls having a leg at the end thereof remote from said shuttle plate for engaging corresponding recesses in the xerographic plate being transported thereby, each of said shuttle plates and said pawls mounted thereon defining a gap therebetween and means for moving said xerographic plate at a first linear velocity through the transfer station; means for feeding a support sheet into image transfer adjacency in the transfer station, said support sheet feeding means including means for moving the support sheet at a second linear velocity during image transfer; means for equalizing the linear velocities of the xerographic plate transporting means and the support sheet feeding means within the transfer station, said velocity equalizing means including an element thereof supported by said plate transporting means and an ele ment thereof supported by said support sheet feeding means, both of said elements being positioned in said gap along the plane passing along the image-bearing surface of the xerographic plate and in contact with each other during image transfer, whereby the xerographic plate and an adjacent support sheet, fed by said support sheet feeding means, are moving at the same linear velocity during image transfer.

10. The image transfer means of claim 9 wherein the linear velocity equalizing element mounted on said plate transporting means comprises a rack and the linear velocity equalizing element mounted on said support sheet feeding means comprises a gear segment, said rack and said gear segment positioned to mesh with each other as the xerographic plate and the support sheet are advanced through the transfer station.

11. The image transfer means of claim 10 wherein said means for moving said xerographic plate at a first linear velocity includes a first motor, said means for moving the support sheet at a second linear velocity during image transfer includes a second motor, and said velocity equalizing means including means permitting said first motor or said second motor to overdrive the other of said motors.

12. The image transfer means of claim 11 wherein said first motor drives said plate transporting means faster than said second motor drives said support sheet feeding means; said overdrive permitting means comprising clutch means associated with said second motor.

13. The image transfer means of claim 10 wherein said support sheet feeding means is driven faster than said plate trans orting means; each shuttle plate has a slot therein, each slot having spaced ends connected together by an elongated passageway, at least one sprocket wheel at each of two terminal positions, endless drive chain means passing around and engaging said sprocket wheels, means to drive said drive chain in one direction only, a pin securely mounted on each endless drive chain associated with said drive chain means, each pin adapted to extend into the slot in the shuttle plate adjacent thereto whereby contact of said pin against one of the surfaces of said slot causes the xerographic plate to be transported along the path through the transfer station; said velocity equalizing means including means permitting said plate transporting means to overdrive said support sheet feeding means, said overdrive permitting means comprising a leg on each of said slots, each leg being parallel to the image-bearing surface of the xerographic plate and extending toward the trailing edge of said xerographic plate transporting means, each of said legs adapted to receive said pin adjacent thereto as said support sheet feeding means overdrives said plate transporting means during image transfer.

14. The image transfer means of claim 13 wherein said leg is perpendicular to said passageway.

15. The image transfer means of claim 14 wherein said leg is connected to said slot adjacent the upper end thereof.

16. The image transfer means of claim 14 wherein said leg is connected to said slot adjacent the lower end thereof.

17. The image transfer means of claim 9 further including means for actuating the motor associated with said support sheet feeding means whereby said plate transporting means and said support sheet feeding means move in synchronization through the transfer station.

18. The image transfer means of claim 17 wherein said actuating means comprises an arm on said support sheet feeding means extending into the path of travel of said plate transporting means, said arm adapted to be contacted by said plate transporting means as said plate transporting means enters the transfer station.

19. The image transfer means of claim 17 wherein said actuating means comprises an arm on said plate transporting means, said arm adapted to contact a switch associated with said support sheet feeding means whereby the motor associated with said support sheet feeding means is activated.

References Cited UNITED STATES PATENTS 3,060,131 10/1962 Crumrine et al. 3S5-l4 X SAMUEL S. MATTHEWS, Primary Examiner R. P. GREINER, Assistant Examiner i US. Cl. X.R. 

